<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>块元素的垂直居中</title>

    <style>
        .div{
            width: 300px;
            height: 300px;
            background-color: blueviolet;
            position: absolute;
            top: 50%;
            transform: translateY(-50%);
        }
    </style>
</head>
<body>
    <div class="div"></div>
</body>
</html>